# Fish Explain

> Clear, expert guides to fish species, care and aquariums


## Posts

- [How to Cycle a Fish Tank: Fishless and Fish-In Methods](https://fishexplain.com/how-to-cycle-a-fish-tank/): Learn how to cycle a fish tank step by step with the fishless or fish-in method, how long tank cycling takes and the test readings that mean it is ready.
- [Cool Freshwater Fish: 20 Unusual Species for Your Aquarium](https://fishexplain.com/cool-freshwater-fish/): Discover 20 cool freshwater fish, from elephantnose fish to glass catfish, with adult size, tank size and care level to help you pick an unusual species.
- [The Aquarium Nitrogen Cycle Explained Simply](https://fishexplain.com/nitrogen-cycle-aquarium/): Learn how the aquarium nitrogen cycle turns toxic ammonia into nitrate, how long cycling takes, safe test levels and how to fix a crashed cycle.
- [Large Fish Tanks: Best Sizes, Setup Tips and Costs](https://fishexplain.com/large-fish-tank/): Planning a large fish tank? Compare 75 to 180 gallon sizes, weights and footprints, plus setup tips and a worked monthly running cost example.
- [Tropical Freshwater Fish: 25 Colorful Species for a Heated Tank](https://fishexplain.com/tropical-freshwater-fish/): Compare 25 tropical freshwater fish for a heated tank, with adult size, tank size and temperature for each, plus tips on choosing tank mates.
- [Fish Tank With Stand: What to Look For Before You Buy](https://fishexplain.com/fish-tank-with-stand/): Buying a fish tank with stand? Check footprint, weight rating, materials and leveling so your aquarium stays safe. Includes a tank weight chart.
- [How to Set Up a Fish Tank: A Beginner's Step by Step Guide](https://fishexplain.com/how-to-set-up-a-fish-tank/): From choosing the spot to adding your first fish, follow these 10 steps to set up a freshwater fish tank the right way, including how to cycle the water safely.
- [Fish Tank Heater Guide: Types, Placement and Best Temperature](https://fishexplain.com/fish-tank-heater/): Tropical fish need warm, steady water. Learn which aquarium heater type to buy, how many watts your tank needs, where to place it and the best temperature for common fish.
- [Best Freshwater Fish for Fish Tanks: 30 Species for Every Setup](https://fishexplain.com/freshwater-fish-for-fish-tanks/): From tiny ember tetras to showpiece discus, these 30 freshwater fish suit home aquariums of every size. Compare adult size, tank size, temperature and temperament, then plan a community that thrives.
- [How to Choose a Fish Tank: Sizes, Types and Buying Guide](https://fishexplain.com/fish-tank-buying-guide/): The right tank makes fishkeeping easier from day one. Compare tank sizes, shapes and materials, see what equipment you need and use our checklist to buy an aquarium fish tank that suits your fish.
- [Wahoo (Ono) Fish: Facts, Taste and How It Is Caught](https://fishexplain.com/wahoo-fish/): Wahoo, called ono in Hawaii, is one of the fastest fish in the ocean and one of the best tasting. Here are the key facts about this sleek mackerel relative, what its meat tastes like and how anglers catch it.
- [Basa vs Swai Fish: What They Are and Are They Safe to Eat?](https://fishexplain.com/basa-vs-swai-fish/): Basa and swai are two closely related catfish farmed in Vietnam and sold as mild, cheap white fillets. Here is how they differ, how they are farmed and inspected, and how to buy and cook them safely.
- [Lowest Mercury Fish: Safest Choices to Eat and Ones to Limit](https://fishexplain.com/lowest-mercury-fish/): Salmon, sardines, anchovies, shrimp, pollock and tilapia are among the lowest mercury fish you can buy. Here is how mercury gets into fish, which seafood to choose most often and which to limit or avoid.
- [Fish Poop: What Healthy and Unhealthy Fish Waste Looks Like](https://fishexplain.com/fish-poop/): Healthy fish poop is short, matches the color of the food and sinks or breaks apart quickly. Here is what white, stringy, long or red fish poop can mean, and what to do about each one.
- [Discus Fish Tank Setup: Water, Size and Tank Mates](https://fishexplain.com/discus-fish-tank-setup/): Discus need warm, soft, very clean water and a tall tank big enough for a group. Here is how to size the tank, dial in the water, choose equipment and pick tank mates that can handle the heat.
- [Severum Fish: Care, Tank Mates and Breeding Guide](https://fishexplain.com/severum-fish/): Severums are calm, long-lived South American cichlids that grow to about 8 inches. Here is how to set up their tank, choose safe tank mates, feed them well and breed a pair at home.
- [Koi Fish Meaning: Colors, Yin Yang Symbolism and Cultural History](https://fishexplain.com/koi-fish-meaning/): Koi stand for perseverance, good fortune and love. Here is what each koi color means, the story behind the yin yang koi, and how these fish moved from Chinese legend to Japanese ponds.
- [Can Fish Blink or Close Their Eyes? How Fish See and Sleep](https://fishexplain.com/can-fish-blink/): Most fish cannot blink because they have no eyelids, so they sleep with their eyes open. Here is which fish can cover their eyes, how fish see underwater and how to tell when your fish is asleep.
- [Are Fish Mammals? How Fish Differ From Whales and Dolphins](https://fishexplain.com/are-fish-mammals/): Fish are not mammals. They breathe with gills, run cold and lay eggs, while whales and dolphins breathe air, keep warm and nurse their calves. Here is how to tell the two apart.
- [Do Fish Have Teeth? Surprising Fish Teeth Facts With Examples](https://fishexplain.com/do-fish-have-teeth/): Nearly every fish has teeth, from a goldfish's hidden throat teeth to a great white's conveyor belt of blades. Here is where fish teeth sit, how they work and which pets can bite.
- [What Do Fish Eat? Diets of Pet, Pond and Wild Fish Explained](https://fishexplain.com/what-do-fish-eat/): Fish diets range from algae and plankton to insects, crabs and other fish. Here is what pet, pond and wild fish eat, how often to feed them and what to keep out of the tank.
- [Unicornfish: Facts, Habitat and Why It Has a Horn](https://fishexplain.com/unicornfish/): Unicornfish are horned relatives of the tangs found on Indo-Pacific reefs. Learn what the horn is for, how to identify the main Naso species, where they live and whether one belongs in your aquarium.
- [Walking Fish: Fish With Legs That Climb, Crawl and Breathe Air](https://fishexplain.com/walking-fish/): Walking fish use fins, fin rays and even gill covers to move over land or along the seafloor. Meet 13 walking fish, learn how they breathe air and see which ones are legal to keep.
- [Rarest Fish in the World: 15 Species Few People Ever See](https://fishexplain.com/rarest-fish-in-the-world/): Meet 15 of the rarest fish in the world, from the Devils Hole pupfish to the coelacanth. See each species' IUCN status, range, threats and what the law says about keeping rare fish.
- [Clownfish Care: Tank Setup, Anemones and How Much They Cost](https://fishexplain.com/clownfish-care/): A complete clownfish care guide covering ocellaris, percula and maroon species, tank setup, water parameters, anemones, pairing, diseases and typical US costs.
- [Freshwater Puffer Fish: Species, Care and Diet Guide](https://fishexplain.com/freshwater-puffer-fish/): Which puffers truly live in fresh water, and how to keep them: nine species compared, tank setup, a snail-based diet, beak trimming, tank mates, toxicity and common diseases.
- [African Cichlids: Care, Tank Setup and Compatible Species](https://fishexplain.com/african-cichlids/): How to keep African cichlids from Lakes Malawi, Tanganyika and Victoria: water chemistry, tank size and rockwork, stocking for aggression, diet by group, compatible species, breeding and common diseases.
- [Cichlid Fish Types: 25 Popular Species and How to Keep Them](https://fishexplain.com/cichlid-fish-types/): Compare 25 popular cichlid fish types by group, from angelfish and rams to Lake Malawi mbuna and Tanganyika shell dwellers, with size, tank, water and temperament for each.
- [Best Nano Fish for Small Tanks: 20 Tiny Species That Thrive](https://fishexplain.com/best-nano-fish-for-small-tanks/): Twenty nano fish compared by adult size, minimum tank, temperature, pH, temperament, group size and care level, with realistic stocking plans for 5, 10 and 20 gallon tanks and a simple cycling guide.
- [Spring or Distilled Water for a Fish Tank? What Is Safe and What Is Not](https://fishexplain.com/spring-or-distilled-water-for-fish-tank/): Distilled water alone is unsafe for fish because it lacks minerals and a pH buffer. Learn when spring water works, how to use distilled or RO water correctly, and why conditioned tap water suits most tanks.
- [Ich on Fish: How to Spot White Spot Disease and Cure It Fast](https://fishexplain.com/ich-on-fish/): How to spot ich on fish, rule out velvet and other lookalikes, and cure white spot disease with heat, salt or medication, plus a treatment timeline and marine ich notes.
- [Common Fish Diseases: Symptoms, Causes and Treatment Chart](https://fishexplain.com/common-fish-diseases/): A symptom-to-treatment chart for 13 common aquarium fish diseases, from ich and fin rot to dropsy and fish TB, with water targets, quarantine setup and safe dosing rules.
- [How Many Fish in a 20 Gallon Tank? Stocking Rules and Sample Setups](https://fishexplain.com/how-many-fish-in-a-20-gallon-tank/): A 20 gallon tank usually holds 10 to 20 small fish, but adult size, bioload, tank shape and schooling needs set the real limit. Here is why the inch-per-gallon rule misleads, plus five sample stocking lists.
- [Best Fish Tank Filters: HOB, Canister and Sponge Filters Compared](https://fishexplain.com/best-fish-tank-filters/): Compare HOB, canister, sponge, internal and undergravel fish tank filters, size flow with the 4 to 6x rule, set up media in the right order and pick the best filter for your tank.
- [Why Is My Fish Tank Cloudy? White, Green and Brown Water Fixed](https://fishexplain.com/cloudy-fish-tank/): White, green or brown water each has a different cause. Here is how to diagnose a cloudy fish tank and clear it safely.
- [Breeding Betta Fish: Pairing, Bubble Nests and Raising Fry](https://fishexplain.com/breeding-betta-fish/): How to breed betta fish: choose and condition a pair, set up a shallow breeding tank, read the bubble nest and spawning signs, and feed and raise the fry.
- [Betta Fish Behavior Before Death: Warning Signs and What You Can Still Do](https://fishexplain.com/betta-fish-behavior-before-death/): Betta fish behavior before death explained: warning signs, how to tell old age from illness or bad water, and the steps you can still take today.
- [Sick Betta Fish: Symptoms, Common Diseases and How to Treat Them](https://fishexplain.com/sick-betta-fish/): How to tell if your betta fish is sick, what the most common betta diseases look like, and how to treat them safely, starting with the water.
- [What Size Tank Does a Betta Fish Need? Why Bowls Fail and 5 Gallons Wins](https://fishexplain.com/betta-fish-tank-size/): How big a tank does a betta fish need? Why bowls and vases fail, why 5 gallons is the real minimum, 5 vs 10 gallons compared, plus water parameters and a setup checklist.
- [Betta Fish Care Guide: Tank, Water, Food and Daily Routine](https://fishexplain.com/betta-fish-care/): Complete betta fish care guide: 5 gallon tank, 76 to 82°F heater, gentle filter, cycling, water parameters, tank mates and a daily care checklist.
- [Best Betta Fish Food: Pellets, Frozen and Live Foods Ranked](https://fishexplain.com/best-betta-fish-food/): Best betta fish food ranked: pellets, frozen and live foods compared by protein, ingredients, portions and safety for healthy bettas.
- [How Often Should You Feed a Betta Fish? Portions, Schedule and Fasting Days](https://fishexplain.com/how-often-to-feed-betta-fish/): How often to feed a betta fish at every age, how many pellets per meal, a sample weekly schedule, fasting days and what to do when your betta will not eat.
- [What Fish Can Live With Bettas? 21 Safe Tank Mates by Tank Size (5 to 40 Gallons)](https://fishexplain.com/what-fish-can-live-with-bettas/): Find out what fish can live with bettas: 21 safe tank mates sorted by tank size, the fish to never add, and how to introduce new tank mates without fights.

## Pages

- [Terms of Use](https://fishexplain.com/terms-of-use/): By using Fish Explain (fishexplain.com), you agree to these Terms of Use. If you do not agree, please do not use the site. Last updated: October 5, 2026.
- [Disclaimer](https://fishexplain.com/disclaimer/): The information on Fish Explain (fishexplain.com) is provided for general educational purposes. Last updated: October 5, 2026.
- [Editorial Policy](https://fishexplain.com/editorial-policy/): Fish Explain exists to give people clear, accurate and useful information about fish.
- [Contact](https://fishexplain.com/contact/): Questions, corrections, topic ideas or partnership requests. Send us a message and a real person will read it.
- [Guides](https://fishexplain.com/guides/)
- [About](https://fishexplain.com/about/): Fish Explain is an independent fish encyclopedia.
- [Home](https://fishexplain.com/): Species profiles, aquarium care and clear answers to the questions people ask about fish. Researched, fact checked and written for curious minds.
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